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So today I finally tackled my rusted out, full of holes, leaking all of the place muffler.
It came off easily enough (a few rusted bolts which were annoying, but I got em off), but I did run into a few snags which prevent me from finishing the job today.
The first, and biggest, snag is that I believe I bought the wrong gaskets to put between the catalytic and the muffler. On RockAuto, it told me to buy Walker 31374 since it is a Walker brand muffler replacement, but as you'll see in the photos below, this gasket is much thicker than the one that came off. Also, it appears to be half solid aluminum on one side and some sort of fabric-y gasket material on the other. When installed, there is a pretty significant "sandwich" between the cat and the muffler due to this larger gasket. Is this the correct gasket? Or do I need a different one? If so, which one? Would I need the same one to reconnect the cat to the header?
Top is the original gasket, bottom is the Walker one Side by side - one is significantly thicker Installed between cat and muffler
Problem #2 - The nuts that held the o2 sensor on the muffler were completely rusted and rounded, so they are pretty much destroyed. What is the correct replacement part number?
Problem #3 - Is there any visual way to check if the o2 sensor needs to be replaced? It definitely looks sooty - pic below - but I'm not getting a CEL or anything.
Those exhaust pipe gaskets are thick off the shelf, and compress substantially during installation. This also makes them hard to re-use and get a successful seal. Pretty much a one shot deal.
I just used the Toyota gaskets. Seem to work fine
part number for the nuts should be 90179-08059
Quick rule of the thumb. If the CEL is off everything is working. Not an ironclad guarantee, but lets me sleep at night.
I don't know much about the muffler stuff. I let Midas do mine. 2 new mufflers on my 87 4Runner, now, second one totally free. I do so love lifetime warranties.
Anywho, on the O2 sensor, if you have ANY doubt about it, replace it. I've put two into my 87 so far simply due to mileage. I think that the FSM I got with the 4Runner specified 60K miles for the O2 sensor replacement. Even if it doesn't, and I can't find where I saw it now, of course, it seems like a decent interval for the sensor replacement. It sure made a big difference in the engine's power, and mileage when I replaced the sensor. Much improved.
Remember to clear the ECU's memory when you change the sensor. It makes it's learning curve shorter. It takes at lease 2 trips for it to start it's learning. 20 miles, I believe. Easy to do. Pull the EFI fuse in the cabin fuse block, IIRC. Might be engine compartment fuse block. I, personally, just pull the negative battery lead for a minute or so, when I do it. Well, changing any electrical part, the negative leads come off the battery until it's totally completed. Just a lot easier for me to do, and to remember where it is You really should pull the negative battery lead when you do go to do replacement of the sensor, anyway.
Finally, then I'll shut up, I ALWAYS put a dab of silicon dielectric grease in any female lead I pull, and plug again. It really helps keep dirt and corrosion to a minimum. That includes plug wires, heck, everything. I love that stuff.
If I were you, I would absolutely replace the O2 sensor. Do NOT go with after market sensors, BTW. Especially Bosch. Those may SAY they're compatible, but they're made for European engines, not Japanese ones, and don't seem to provide the exactly correct outputs to the ECM. Close, but not exactly correct. Get a Japanese made sensor. Aisin, Denso, whatever you can find.
Good luck on the rest. Sorry I wasn't more help...
Pat☺
I don't know much about the muffler stuff. I let Midas do mine. 2 new mufflers on my 87 4Runner, now, second one totally free. I do so love lifetime warranties.
Anywho, on the O2 sensor, if you have ANY doubt about it, replace it. I've put two into my 87 so far simply due to mileage. I think that the FSM I got with the 4Runner specified 60K miles for the O2 sensor replacement. Even if it doesn't, and I can't find where I saw it now, of course, it seems like a decent interval for the sensor replacement. It sure made a big difference in the engine's power, and mileage when I replaced the sensor. Much improved.
Remember to clear the ECU's memory when you change the sensor. It makes it's learning curve shorter. It takes at lease 2 trips for it to start it's learning. 20 miles, I believe. Easy to do. Pull the EFI fuse in the cabin fuse block, IIRC. Might be engine compartment fuse block. I, personally, just pull the negative battery lead for a minute or so, when I do it. Well, changing any electrical part, the negative leads come off the battery until it's totally completed. Just a lot easier for me to do, and to remember where it is You really should pull the negative battery lead when you do go to do replacement of the sensor, anyway.
Finally, then I'll shut up, I ALWAYS put a dab of silicon dielectric grease in any female lead I pull, and plug again. It really helps keep dirt and corrosion to a minimum. That includes plug wires, heck, everything. I love that stuff.
If I were you, I would absolutely replace the O2 sensor. Do NOT go with after market sensors, BTW. Especially Bosch. Those may SAY they're compatible, but they're made for European engines, not Japanese ones, and don't seem to provide the exactly correct outputs to the ECM. Close, but not exactly correct. Get a Japanese made sensor. Aisin, Denso, whatever you can find.
Good luck on the rest. Sorry I wasn't more help...
Pat☺
Hey man - thanks so much for the advice! I'll figure the muffler stuff - gaskets are cheap enough for some trial and error lol.
Would you replace both the upstream and downstream o2s? I have a CA spec truck, so I unfortunately have both. The one pictured is just the downstream one.
Yes, I would. But if you are going to just replace one, the upstream one is the one to go for. It has the greatest effect on the mixture settings the ECU uses.
Oct 23, 2021 | 08:36 PM
You really should pull the negative battery lead when you do go to do replacement of the sensor, anyway.
